How can I import AVCHD?

I've seen some talk of this in other threads but cant solve my problem.

I have saved AVCHD cards on a hard drive. I completely copied the card. I am trying to copy files to my library. I click import+bring files into library....but nothing happens. I have the files in my library, but it's clear it's reading them off the saved card. I have a camera icon in the lower corner, it never imported, and it moves slow. It def convert and import the file.

[Noam Osband]"I have saved AVCHD cards on a hard drive. I completely copied the card. I am trying to copy files to my library. "

Importing them to the library should work, although people sometimes encounter problems with interrupted import which keeps referencing the card. This produces the error "referencing media on the camera". Ben Halsall discusses that in the below video.

[Eric Santiago]"Never had issues with that and at times its the only fast option to get out of that workflow."

There are severe problems if doing "leave files in place" import of bare MTS files from an AVCHD package. You may not notice it at first, but the I/O load can be incredibly high, which can bog down many operations.

Unfortunately macOS no longer permits use of command-line dtrace utilities, but this is an I/O histogram from FCPX when simply scrolling through a library that contains .MTS files imported in place. As you can see it produces a very high number of small I/Os. This is absolutely unique to bare MTS files imported in place: https://joema.smugmug.com/Computers/FCPX-Event-Browser-Perf-Data/n-M7bG7L/i...

The same behavior still exists on FCPX 10.4.7 and Mojave. If already imported one solution is create optimized media. If not yet imported, the best practice is either import only from the AVCHD package, or else externally re-wrap using EditReady.

[Joe Marler]"There are severe problems if doing "leave files in place" import of bare MTS files from an AVCHD package."

I only use "Leave files.." with RED RAW data.
I think I have run into issues in the past with .mts files thus why I got into the habit of pulling them out and converting to ProRes before it hits FCPX.
Im old school that way.

[Eric Santiago]"I think I have run into issues in the past with .mts files thus why I got into the habit of pulling them out and converting to ProRes before it hits FCPX."

You'd likely be better off leaving the .mts files in the AVCHD package... just drop it into EditReady for your ProRes conversion and you retain more metadata, spanned clips are properly identified and reconnected, and you save time not digging those .mts files out of the package. Wins everywhere!

So in the end, I managed to import by going to "Reimport from Cameras." It would only import that way. What it then imported is a MPEG-4 mov file. Should I edit with that or should I bring that to Compressor or turn it into Pro Res? It works fine in FCP X so there's no need to change it for that reason. Thoughts?

I understand it takes more processor overhead to work with the mpeg4 files versus say a prores or dvcproHD file. If that doesn't trouble you, I'd say go ahead. Your final render will possibly be slower. Me, I always bump my mpeg4 to prores before I work with it in FCPX.

There is no difference in image quality for FCPX editing. This is because the MPEG4 media files themselves are not re-written - IOW there is no "generational loss" since FCPX records all edits as metadata in a SQL database. For the final export that must be encoded in the preferred codec, but that would often be required even if you pre-converted the material to ProRes.

If you are working collaboratively with others in a post production pipeline and handing off files, in that case using ProRes can avoid generational loss. Or if you are doing "round trips" to other software, e.g, Resolve, then use ProRes for the same reason.